A hot pack placed on the skin illustrates which mode of heat transfer?

• A. Conduction
• B. Convection
• C. Radiation
• D. Evaporation

Answer: (A)

Direct contact heat transfer, or conduction, is at work when a hot pack sits on the skin. Heat flows from the hotter pack into the cooler skin through their direct contact, driven by the temperature difference and the materials’ ability to conduct heat. The tighter the contact and the higher the pack’s thermal conductivity, the faster the heat transfer.

Convection would require moving air or liquid to carry heat, which isn’t the main mechanism here. Radiation would transfer heat by infrared waves without needing contact, and while you can feel heat from those waves, the hot pack on the skin primarily heats through conduction. Evaporation involves a liquid changing to vapor to absorb heat, which isn’t the core process in this scenario.